Treating high-speed steel



UNITED STATES PATENT OFFICE.

CLARENCE A.

WHITMYRE, or SCHEZN'ECTADY, NEW YORK, ASSIGNOR T0 GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

TREATING HIGH-SPEED STEEL.

No Drawing. I

To all whom it may concern:

Be itknown that I, CLARENCE A. WHIT- MYBE, a citizen of the United States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Treating High-Speed Steel, of which the followlng is a specification.

The present invention relates to the heat treatment of high speed alloy steel and particularly to the quenching of steel after 'having been heated to a high. temperature in order to harden and temper the same.

It is the object of my invention to avoid.

cracks in the hardened steel and to improve the quality of the steel.

Prior to my 1nvent1on it has been customary to heat cutters andsimilar high speed steel tools to a high temperature and then cooling from 1300 C. toroom temperature.

High speed steel, as distinguished from nickel steel, or carbon steel, is characterized by a high tungsten content. A typical high speed steel contains besides iron the following: tungsten 13 to 15%; chromium 3.5

to 4.25%; carbon .55 to .70%; vanadium 1%; silicon 15 to 21%; manganese .20 to 40%; sulfur and'phosphorus being kept negligibly low.

When carrying out my invention the tool to be hardened is first slowly preheated to about 850 C. in any convenient way, say,

for example, in an oil, gas or electric furnace in the usual well understood manner. The tool is then heated from 850 C; as

. rapidly as is desired to 1300 C. in any'suite furnace. When maintained at this temperature range, may

Specification of Letters Patent.

the tool has reached the temperature of 1275 to 1300 C. it is.

- Patented Nov. 23, 1920.

7 Application filed August 2,1919. Serial No. 314,968.

be used, but I prefer to employ a bath consisting of the chlorids of potassium, sodium, calcium and barium used in equal proportions by weight. When the high speed steel tool has attained the temperature of this quenching bath, it is removed and allowed to cool in the air. If desired, the hardened tool may be subsequently heated or drawn to remove strains in the usual manner.

' What I claim as new and desire to secure by Letters Patent of the United States, is,- 1. The method of hardening high speed steel which consists in heating the steel to a temperature of about 1275 to 1300 C. and then quenching the same at temperature of about GOO-650 C.

2. The method of quenching alloy steel which consists in heating the steel to atemperature of about 1275 to 1300 C. and then reducing the temperature of said steel to about 600 to 650 C. by contact with a bath of fused salts.

3. The method of hardening tungsten steel which consists in'heating steel to a temperature of about 127 5 to 1300 C. and

then quenching the heated steel by contact with a bath of molten chlorids of potassium, sodium, calcium and barium in equal proportions by weight, said bath being heated to a temperature of about 600- 650 C.

LA quenching bath for high speed steel consisting of the chlorids of potassium,

. sodium, calcium and barium in proportionsv adapted to cause said ba-th' to be liquid at.

about 600 to 650 C.

5. A quenching bath for high speed steel consisting of the chlorids ofpotassium, sodium, calcium and barium inequal proportions by weight.

6. The method of hardening steel tools containing at least about 13% tungsten, which consists in slowly heating. said tools to about 850 0., then rapidly :raising the temperature of said tool to about 1300 C., thereupon quenching the heated tool in a bath of fused salts maintained at a temperature of about 600 to 650 C. and finally permitting' said tool to cool in the air.

In witness whereof, I have hereunto set my'hand this 1st day of August, 1919. 

